ST. LOUIS — Sandy Alderson might have a better chance of finding Jimmy Hoffa than a dependable closer for the Mets before next season.

The Mets general manager hasn’t given up on identifying an internal candidate to fill the team’s ninth-inning void heading to 2012, but he is willing to admit the experiment hasn’t gone so smoothly.

The presumed heir apparent, Bobby Parnell, has flopped and a fatigued Pedro Beato never really entered the equation. Manny Acosta has shown flashes of dominance, but there are still organizational questions about his makeup.

It has left Alderson far from certain the next Mets closer will come from within the organization.

“I’m not convinced of that,” Alderson said before the Mets departed Atlanta on Sunday. “Nor can I believe anybody else is convinced of that.”

If Alderson had money to spend this winter, he might take a serious look at potential free agents such as Heath Bell, Jonathan Broxton and Jonathan Papelbon. But with the GM on record as saying the Mets’ payroll could drop $30-40 million next year, a big splash for a closer doesn’t seem likely, especially if the club is serious about re-signing Jose Reyes.

But that doesn’t mean Alderson doesn’t value having a quality closer.

“I think [closer] is a spot where a team has to have some confidence that those saves are going to be converted, routinely and at a certain level,” Alderson said. “There is a difference between blowing a save every once and a while and blowing them quite often. I think that can have a very negative effect in a cumulative sense.”

The likely scenario has the Mets acquiring a cheap, proven veteran and hoping they get lucky — in much the same manner they did with Jason Irsinghausen this year. The 39-year-old Isringhausen, who became the closer for a month after Francisco Rodriguez was traded, wants to pitch again next season, but the Mets are wary of his health. The righty stayed healthy for most of this season before incurring a herniated disk that has sidelined him for the last two weeks.

Alderson was asked if he’s bothered that an internal candidate for closer hasn’t emerged.

“I’m not troubled by it,” Alderson said. “One of the reasons that you try a variety of possibilities is to sort through it all. We know more than we did a month and a half ago, and that is a good thing.”

Alderson wouldn’t completely rule out the possibility of converting a starting pitcher such as Mike Pelfrey into a closer, but said it’s not the preferred solution.

Maybe the only guarantee regarding next season’s bullpen is the inclusion of lefty reliever Tim Byrdak, who signed a one-year contract extension on Sunday. Acosta also has positioned himself for a job. Ineffective D.J. Carrasco has a year remaining on his contract.

Alderson said strengthening the bullpen as a whole will be an emphasis this winter — Mets relievers have a 4.22 ERA, which ranks last in the National League.

“It can be unpredictable,” Alderson said, referring to building a bullpen. “But one has to account for that unpredictability, which means you have to have lots of options. You have to have flexibility. You have to have players that can go to Triple-A and come back. But you also have to hit on two or three guys that can be effective for you.

“I kind of look at our bullpen pre-Frankie [Rodriguez] trade and after. It was decent before the trade, but after that time, it hasn’t been as good.”